One driver having external electrodes arranged over both surfaces of a piezoelectric ceramic plate polarized in the direction of its thickness, and one generator having two mutually opposed interdigital electrodes on one or both surfaces of a piezoelectric ceramic plate and alternately polarized in the direction of its length between the electrode fingers of the interdigital electrodes are formed combined in alignment in the direction of the length of the piezoelectric ceramic plate. Alternatively, the driver and generator may be formed in alignment in the direction of the width of piezoelectric ceramic plate. By applying a low voltage to this piezoelectric ceramic transformer from the driver at a resonance frequency of a longitudinal vibration of second order mode of the piezoelectric ceramic plate, a high voltage can be picked up from the generator. Here, through connection of the input terminals and output terminals at the nodes of vibration, failure due to vibration of lead wires can be prevented, thereby obtaining a compact and slim transformer element that provides high reliability. A plurality of drivers and generators may also be employed, and in addition, an interdigital electrode may be used in the driver as well as in the generator.